This invention relates generally to a method and apparatus for making electrical harnesses having a predetermined number of terminals, and more particularly, to an automatic method and apparatus for positioning at a terminating station each portion of the wire to have a terminal attached, displacing the insulation from that portion of the wire's conductor to bare the underlying conductor, attaching a terminal to the conductor, and cutting off the wire from its supply or otherwise removing the wire from the apparatus to complete the harness after the pre-determined number of terminals have been attached.
Lead wires are commonly used to make interconnections between two separate and spaced-apart contact points. The electrical connections are made by placing the lead wire terminal connector onto the electrical unit's mating connector which is located on the outside of the unit. The lead wire terminal connector typically is a female member and the electrical unit's connector is a male member, such as a blade contact. Electrical connections are made quickly and simply by slipping the female member onto the blade contact. Such lead wire interconnections are used, for example, in control panels such as those in household appliances wherein several switches, indicator lights, etc., are clustered together and require interconnection to a common power source.
In the prior art, lead wires are typically made by cutting electrical wire into specific lengths, stripping the insulation from the ends of the wire conductor and attaching terminals to the ends of the conductor. In more automated prior art devices, a continuous length of insulated wire has its insulation removed at spaced locations and then the wire is cut into specific lengths where the insulation has been removed. This produces specific lengths of wire with a bared conductor at each end to which a terminal can be attached. U.S. Pat No. 3,364,801 is an example of this process wherein the wire is fed from a supply reel and the removal of the insulation is controlled electronically. U.S. Pat. No. 3,769,681 discloses a high speed wire cutter for forming specific lengths of wire and an insulation stripping apparatus joined by a conveyor with a terminal device for attaching terminals to the end of the wire. Several other automatic devices for performing center stripping, cutting and feeding of wire in various sequential combinations for lead wires with terminals on their ends have been disclosed. Examples of these are U.S. Pat. Nos. 2,934,982 and 3,162,391. U.S. Pat. No., 3,095,768 shows a tape control version of these operations. Hand tools also are known which physically remove insulation from the ends of wire. Such a tool is disclosed in U.S. Pat. No. 1,396,903.
Lead wires, per se, have been replaced by electrical harness units where appropriate. Harnesses, which represent a different approach to electrical interconnecting, are particularly useful in an environment where the electrical units to be interconnected are many and fairly close to one another. The terminals are spaced on the harness unit to match the spacing between the electrical unit's contact points that are to be interconnected. One example of such a harness is the "daisy chain" type of harness wherein a number of terminal connectors are joined together by a section of insulated wire. The terminals are spaced from one another by predetermined distances to accommodate the distance between the contact points to which they are to be attached. In this type of harness, the electrical current can be applied at one end of the harness and fed to all of the terminals directly through the harness. The main advantages of this type of harness is that it is relatively easy to install and it takes up less room when compared to the individual lead wire approach.
One drawback with such harnesses, however, is that there is not available a truly automatic way of repetitively manufacturing the complete harness. At the present time, harnesses are manufactured in a number of individual operations, many of which are manual in nature. Because of this, harnesses are relatively expensive and time-consuming to manufacture. In addition, there is a need for many different types of harnesses and the changeover from one harness configuration to another in the manufacturing environment is also time-consuming and expensive.
Harnesses are also typically made up of individual sections of insulated wire resulting in a large number of electrical discontinuities in the harness unit. Discontinuities are those areas at which the wire is broken to have a terminal connected thereto. These are particularly to be avoided in electrical interconnections because of their greater potential to fail. They generate greater temperatures and, consequently, can cause the circuits to rapidly deteriorate and become inoperative.
Accordingly, it is a primary object of the present invention to improve the method and apparatus for manufacturing electrical harnesses.
It is another object of the present invention to substantially reduce the number of discontinuities in electrical harnesses.
It is another object of the present invention to provide a pre-programmable automatic machine to manufacture electrical harnesses.
It is another object of the present invention to lower production costs in the manufacture of electrical harnesses.
It is another object of the present invention to save space in the manufacturing of electrical harnesses.
It is another object of the present invention to improve the quality of electrical harnesses.
It is another object of the present invention to manufacture electrical harnesses which are easier to route and trace to the contact points.
It is another object of the present invention to improve the speed at which electrical harnesses can be manufactured.
It is another object of the present invention to provide a harness manufacturing method and apparatus which can be rapidly modified in changing from one harness configuration to another.